Home About us Contact
|
Home About us Contact | ||
|
|
||
Fluorescence Spectrometry (fluorescence + spectrometry)
Kinds of Fluorescence Spectrometry Selected AbstractsComparison of Linear Regression Models for Quantitative Geochemical Analysis: An Example Using X-Ray Fluorescence SpectrometryGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 3 2005Mirna Guevara calibration analytique; régression linéaire; matériaux de référence en géochimie; géochimie analytique; loi de propagation d'erreurs This paper presents statistical aspects related to the calibration process and a comparison of different regression approaches of relevance to almost all analytical techniques. The models for ordinary least-squares (OLS), weighted least-squares (WLS), and maximum likelihood fitting (MLF) were evaluated and, as a case study, X-ray fluorescence (XRF) calibration curves for major elements in geochemical reference materials were used. The results showed that WLS and MLF models were statistically more consistent in comparison with the usually applied OLS approach. The use of uncertainty on independent and dependent variables during the calibration process and the calculation of final uncertainty on individual results using error propagation equations are the novel aspects of our work. Cet article présente les aspects statistiques liés au processus de calibration et fait une comparaison des différents calculs de régression utilisés dans pratiquement toutes les techniques analytiques. Les modèles des moindres carrés ordinaires (MCO) et pondérés (MCP), et d'ajustement de maximum de vraisemblance (AMV) ont étéévalués et appliqués aux courbes de calibration d'éléments majeurs obtenues en analyse par fluorescence X (XRF) de matériaux certifiés de référence. Les résultats obtenus avec les modèles MCP et AMV sont plus cohérents statistiquement que ceux obtenus la méthode classique des MCO. L'utilisation de l'incertitudes sur des variables indépendantes ou dépendantes durant la procédure de calibration et le calcul de l'incertitude finale sur chaque résultat à partir des lois de propagation d'erreur sont des aspects novateurs de ce travail. [source] Trace Elemental Analysis of Titanium Dioxide Pigments and Automotive White Paint Fragments for Forensic Examination Using High-Energy Synchrotron Radiation X-Ray Fluorescence Spectrometry,JOURNAL OF FORENSIC SCIENCES, Issue 3 2009Yoshinori Nishiwaki M.S. Abstract:, High-energy synchrotron radiation x-ray fluorescence spectrometry (SR-XRF) utilizing 116 keV x-rays was used to characterize titanium dioxide pigments (rutile) and automotive white paint fragments for forensic examination. The technique allowed analysis of K lines of 9 trace elements in 18 titanium dioxide pigments (rutile), and 10 trace elements in finish coat layers of seven automotive white paint fragments. High-field strength elements (HFSE) were found to strongly reflect the origin of the titanium dioxide (TiO2) pigments, and could be used as effective parameters for discrimination and classification of the pigments and paint fragments. A pairwise comparison of the finish coat layers of seven automotive white paint fragments was performed. The trace elements in the finish coat layers detected by the high-energy SR-XRF were especially effective for identification. By introducing the trace element information of primer and electrocoat layers, all the automotive white paint fragments could be discriminated by this technique. [source] In-situ gamma-ray spectrometric study of weathered volcanic rocks in Hong KongEARTH SURFACE PROCESSES AND LANDFORMS, Issue 6 2002Margie Q. F. Chen Abstract In-situ gamma-ray spectrometry (GRS) measurements were conducted at 35 sites in Hong Kong where volcanic rocks with varying extent of weathering were exposed. Elemental analyses using X-ray fluorescence spectrometry and inductively coupled plasma,mass spectrometry were carried out on samples collected from these 35 plus 22 other locations to assess the feasibility of using the GRS method to quantify the extent of weathering. The Parker weathering index, varying within a range of 0·0,0·8 for the samples studied, was used as a geochemically based reference scheme for correlating the gamma-ray spectrometric results with the extent of weathering. For the former 35 sites, the concentrations of the three major radioelements, K, U and Th, determined by in-situ GRS were compared to laboratory-determined values from the samples. The study reveals that no significant change occurs to the contents of the three radioelements during the initial state of weathering. But once the rocks become highly weathered, further progression of weathering is accompanied by a systematic removal of K and an increased dispersion of U and Th. The results show that K content, which is indicative of the extent of weathering, can be retrieved reliably with the gamma-ray spectrometry technique. The study has given support to the potential use of the downhole spectral gamma method for evaluation of weathering grade and the detection of subsurface clay-rich levels. Copyright © 2002 John Wiley & Sons, Ltd. [source] Novel Thorium Membrane Sensors with Anionic Response Based on Trioctylphosphine Oxide and Toluate IonophoresELECTROANALYSIS, Issue 19 2008Abstract Two novel potentiometric polymeric membrane sensors for rapid and accurate determination of thorium are described. These are based on the use of trioctylphosphine oxide (TOPO) and thorium toluate (Th-TA) as ionophores dispersed in poly(vinyl chloride) matrix membranes plasticized with nitrophenyloctyl ether. In strong nitric acid medium, Th(IV) nitrate is converted into [Th(NO3)6]2, complex and sensed as anionic divalent ion which exclude most cationic effect. Validation of the assay methods using the quality assurance standards (linearity range, accuracy, precision, within-day variability, between-day-repeatability, lower detection limit and sensitivity) reveals excellent performance characteristics of both sensors. The sensors exhibit near-Nernstian response for 1.0×10,6,1.0×10,1 M Th over the pH range 2.5,4.5. Calibration slopes of ,32.3±0.3 and ,27.2±0.2,mV/decade, precision of ±0.5 and ±0.8% and accuracy of 98.8±0.9 and 97.9±0.7% are obtained with TOPO and Th-TA based sensors, respectively. Negligible interferences are caused by most interfering mono-, di-, tri-, tetra-, penta-, and hexa-valent elements commonly associated with thorium in naturally occurring minerals and ores. High concentrations of Cl,, F,, SO42,, and NO3, ions have no diverse effect. Complete removal of the effect of the interferents in complex matrices is achieved by retention of [Th(NO3)6]2, complex from 5,M nitric acid/methanol mixture (1,:,9,v/v) on a strong anion exchanger, washing out the cationic interferents followed by stripping off thorium anion complex and measurements. Both sensors are used for determining thorium in certified thorium ore samples (20,120,mg Th/kg) and some naturally occurring ores (200,600,mg Th/kg). The results obtained agree fairly well with the certified labeled values or the data obtained using X-ray fluorescence spectrometry [source] Mercury speciation by CE: An updateELECTROPHORESIS, Issue 1 2009Petr Kubán Abstract This review provides an update on mercury speciation by CE. It includes a brief discussion on physicochemical properties, toxicity and transformation pathways of mercury species (i.e. methyl-, ethyl-, phenyl- and inorganic mercury) and outlines recent trends in Hg speciation by CE. CE is presented as a complementary technique to chromatographic separation techniques, especially in cases when speed, high efficiency and low sample volumes are required. The development of suitable sample preconcentration/isolation (sample stacking, ion exchange, liquid,liquid,liquid extraction, dual-cloud point extraction) to achieve low LODs for analysis of trace concentrations of mercury species in real samples is emphasized. Hyphenation of CE to element specific detectors (i.e. electrothermal atomic absorption spectrometry, atomic fluorescence spectrometry, inductively coupled plasma-optical emission spectrometry, inductively coupled plasma-mass spectrometry) is discussed as well as a potential of CE in interaction studies that may provide useful information on interaction of various Hg species with selected bio-macromolecules. [source] Development of a new hybrid technique for rapid speciation analysis by directly interfacing a microfluidic chip-based capillary electrophoresis system to atomic fluorescence spectrometryELECTROPHORESIS, Issue 11 2005Feng Li Abstract This paper represents the first study on direct interfacing of microfluidic chip-based capillary electrophoresis (chip-CE) to a sensitive and selective detector, atomic fluorescence spectrometry (AFS) for rapid speciation analysis. A volatile species generation technique was employed to convert the analytes from the chip-CE effluent into their respective volatile species. To facilitate the chip-CE effluent delivery and to provide the necessary medium for subsequent volatile species generation, diluted HCl solution was introduced on the chip as the makeup solution. The chip-CE-AFS interface was constructed on the basis of a concentric "tube-in-tube" design for introducing a KBH4 solution around the chip effluent as sheath flow and reductant for volatile species generation as well. The generated volatile species resulting from the reaction of the chip-CE effluent and the sheath flow were separated from the reaction mixture in a gas-liquid separator and swept into the AFS atomizer by an argon flow for AFS determination. Inorganic mercury (Hg(II)) and methylmercury (MeHg(I)) were chosen as the targets to demonstrate the performance of the present technique. Both mercury species were separated as their cysteine complexes within 64 s. The precision (relative standard deviation, RSD, n = 5) of migration time, peak area, and peak height for 2 mg·L,1 Hg(II) and 4 mg·L,1 MeHg(I) (as Hg) ranged from 0.7 to 0.9%, 2.1 to 2.9%, and 1.5 to 1.8%, respectively. The detection limit was 53 and 161 µg·L,1 (as Hg) for Hg(II) and MeHg(I), respectively. The recoveries of the spikes of mercury species in four locally collected water samples ranged from 92 to 108%. [source] Molecular weight and humification index as predictors of adsorption for plant- and manure-derived dissolved organic matter to goethiteEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2007T. Ohno Summary Sorptive retention of organic matter is important in maintaining the fertility and quality of soils in agricultural ecosystems. However, few sorption studies have been conducted that use dissolved organic matter (DOM) characteristic of agricultural amendments. We investigated the sorption to goethite (,-FeOOH) of DOM extracted from: (i) above-ground biomass of wheat straw (Triticum aestivum L.), maize residue (Zea mays L.), soybean residue (Glycine max (L.) Merr.), and hairy vetch residue (Vivia billosa L.); (ii) below-ground biomass from maize, soybean, canola (Brassica napus L.), and green bean (Phaseolus vulgaris L.); and (iii) beef, dairy, poultry, and pig animal manures. The apparent molecular weight (MWAP) of the DOM was measured by high performance-size exclusion chromatography and ranged from 312 to 1074 g mol,1. The carboxyl-group content of the DOM measured by potentiometric titration ranged from 4.84 to 21.38 mmol(,) g,1 carbon. The humification index (HIX) determined by fluorescence spectrometry varied from 1.15 to 4.33. Sorption was directly related to both MWAP and HIX values of the DOM. Molecular weight analysis of the solution prior to and after sorption indicated that the DOM molecules > 1800 g mol,1 were preferentially sorbed, resulting in fractionation of the DOM upon reaction with goethite. The multiple regression equation, based only on MWAP and HIX parameters, explained 76% of the variance in amount of DOM sorbed. The results indicate that MWAP and HIX are important factors in controlling the sorption of DOM to mineral surfaces. Amendment with materials that release DOM of higher molecular weight and greater humification will result in enhanced initial sorption of DOM to soil solids, thereby contributing to accumulation of a larger soil organic C pool. [source] Neutron Activation Analysis, Atomic Absorption and X-Ray Fluorescence Spectrometry Review for 2003GEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 1 2005L. Paul Bédard This review for the year 2003 deals with three relatively well-established, mature, analytical techniques (neutron activation analysis, atomic absorption spectrometry and X-ray fluorescence spectrometry) that nevertheless remain very important for the characterisation of geological and environmental samples. Developments in neutron activation analysis included modification to the technique in relation to the determination of platinum-group elements, as well as consideration of sample size in ore grade estimation. A considerable body of literature was published on the application of atomic absorption spectrometry in the analysis of environmental samples. Many of these proposed technical and methodological improvements, notably in extraction procedures. X-ray fluorescence spectrometry saw developments in in situ analysis, synchrotron micro-XRF (,-SRXRF) and a confocal X-ray set-up for 3D elemental imaging. XRF technologies were used in the analysis of geological samples, reference materials, glasses, solutes and environmental materials. [source] In vitro degradability and stability of hydrophobically modified pH-sensitive micelles using MPEG-grafted poly(,-amino ester) for efficient encapsulation of paclitaxelJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Min Sang Kim Abstract Methoxypoly(ethylene glycol)-grafted poly(,-amino ester) was synthesized for the fabrication of pH-sensitive micelles, and these micelles were modified with deoxycholic acid to facilitate the hydrophobic interaction between the micellar core and paclitaxel. The micelle properties were studied by dynamic light scattering and fluorescence spectrometry. An in vitro degradation study showed that the synthesized polymers degraded hydrolytically within 24 h under physiological conditions. The stability of paclitaxel-loaded pH-sensitive micelles was evaluated in vitro. The introduced deoxycholic acid more stabilized the micelles at pH 7.4 compared to the micelles without modification. But the pH-sensitive region of the micelles was lowered from pH 6.8 to pH 5.8. These results indicate that pH-sensitive micelles with improved stability have great potential as hydrophobic drug carriers for tumor targeting. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Analysing metals in bottle-grade poly(ethylene terephthalate) by X-ray fluorescence spectrometryJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Wanderson Romão Abstract After a rigorous cleaning process, recycled food-grade poly(ethylene terephthalate) (PET), can be mixed with virgin PET resin in different concentrations and used for packaging of soft drinks. Therefore, it is important to have an experimental method to distinguish the presence of recycled polymer in a batch and to check its "true quality." One of the issues to be verified is the presence of inorganic contaminants due to the recycling process. X-ray fluorescence technique is one alternative for this kind of analysis. The results obtained in this work show that bottle-grade PET samples (PET-btg) are made either via direct esterification or by a transesterification process. Samples that were subjected to thermo-mechanical processings (superclean® processing, PET-btg blends processed in our laboratory and soft drink PET packaging) present Fe K, emission lines with higher intensities than those presented by virgin bottle-grade PET. After applying principal component analysis, it can be concluded that Fe is an intrinsic contaminant after the recycling process, furnishing a way to indicate class separations of PET-btg. A calibration and validation partial least squares model was constructed to predict the weight percent of post-consumption bottle-grade PET in commercial PET samples. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Trace Elemental Analysis of Titanium Dioxide Pigments and Automotive White Paint Fragments for Forensic Examination Using High-Energy Synchrotron Radiation X-Ray Fluorescence Spectrometry,JOURNAL OF FORENSIC SCIENCES, Issue 3 2009Yoshinori Nishiwaki M.S. Abstract:, High-energy synchrotron radiation x-ray fluorescence spectrometry (SR-XRF) utilizing 116 keV x-rays was used to characterize titanium dioxide pigments (rutile) and automotive white paint fragments for forensic examination. The technique allowed analysis of K lines of 9 trace elements in 18 titanium dioxide pigments (rutile), and 10 trace elements in finish coat layers of seven automotive white paint fragments. High-field strength elements (HFSE) were found to strongly reflect the origin of the titanium dioxide (TiO2) pigments, and could be used as effective parameters for discrimination and classification of the pigments and paint fragments. A pairwise comparison of the finish coat layers of seven automotive white paint fragments was performed. The trace elements in the finish coat layers detected by the high-energy SR-XRF were especially effective for identification. By introducing the trace element information of primer and electrocoat layers, all the automotive white paint fragments could be discriminated by this technique. [source] Synthesis and supramolecular self-assembly of thermosensitive amphiphilic star copolymers based on a hyperbranched polyether coreJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2008Haiyan Hong Abstract A novel amphiphilic thermosensitive star copolymer with a hydrophobic hyperbranched poly (3-ethyl-3-(hydroxymethyl)oxetane) (HBPO) core and many hydrophilic poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) arms was synthesized and used as the precursor for the aqueous solution self-assembly. All the copolymers directly aggregated into core,shell unimolecular micelles (around 10 nm) and size-controllable large multimolecular micelles (around 100 nm) in water at room temperature, according to pyrene probe fluorescence spectrometry and 1H NMR, TEM, and DLS measurements. The star copolymers also underwent sharp, thermosensitive phase transitions at a lower critical solution temperature (LCST), which were proved to be originated from the secondary aggregation of the large micelles driven by increasing hydrophobic interaction due to the dehydration of PDMAEMA shells on heating. A quantitative variable temperature NMR analysis method was designed by using potassium hydrogen phthalate as an external standard and displayed great potential to evaluate the LCST transition at the molecular level. The drug loading and temperature-dependent release properties of HBPO- star -PDMAEMA micelles were also investigated by using indomethacin as a model drug. The indomethacin-loaded micelles displayed a rapid drug release at a temperature around LCST. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 668,681, 2008 [source] Pyrromethene dye sensitized photopolymer,photochemical behavior in polymer matrix and application to photoresist for printed circuit boardPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 5 2006Shota Suzuki Abstract The photochemical behavior of the visible light initiating system that consists of a sensitizing dye, 2,6-diethyl-8-phenyl-1,3,5,7-tetramethylpyrromethene BF2 complex (EPP), and a photoacid generator, N -trifluoromethylsulfonyloxy-1,8-naphthalimide (NIOTf), was studied mainly by means of absorption and fluorescence spectrometry not in solution but in a polymer matrix which is a closer medium to the one currently employed in the field of photoresists. Excited singlet electron transfer from EPP to NIOTf was considered as the main reaction pathway in this system. The EPP/NIOTf system was applied to a photoresist for printed circuit board with an appropriate binder polymer which contains an acetal protection group. A pattern profile of the photoresist was exceedingly affected by the amount of photogenerated acids, their diffusion, and amine in the atmosphere. Finally, by controlling exposure energy and the post-exposure bake (PEB) process, a photoresist with a high resolution (8,µm line and space) was obtained under argon ion laser irradiation. Copyright © 2006 John Wiley & Sons, Ltd. [source] Arsenic and thallium data in environmental samples: Fact or fiction?REMEDIATION, Issue 4 2010Susan D. Chapnick Matrix effects may increasingly lead to erroneous environmental decisions as regulatory limits or risk-based concentrations of concern for trace metals move lower toward the limits of analytical detection. A U.S. Environmental Protection Agency Office of Technical Standards Alert estimated that environmental data reported using inductively coupled plasma spectrometry (ICP-AES) has a false-positive rate for thallium of 99.9 percent and for arsenic of 25 to 50 percent. Although this does not seem to be widely known in the environmental community, using three case studies, this article presents data in environmental samples that demonstrate severe matrix effects on the accuracy of arsenic and thallium results. Case Study 1 involves soil results with concentrations that approached or exceeded the applicable regulatory soil cleanup objectives of 13 mg/kg for arsenic and 2 mg/kg for thallium. Reanalysis using ICP coupled with a mass spectrometer (ICP-MS) confirmed all thallium results were false positives and all arsenic results were biased high, concluding no action was required for soil remediation. Case Study 2 involves groundwater results for thallium at a Superfund site, where thallium was detected in groundwater up to 21.6 , g/L using ICP-AES. Reanalysis by ICP-MS reported thallium as nondetect below the applicable regulatory level in all samples. ICP-MS is usually a more definitive and accurate method of analysis compared to ICP-AES; however, this is not always the case, as we demonstrate in Case Study 3, using data from groundwater samples at an industrial site. Through a weight-of-evidence approach, it is demonstrated that although method quality control results were acceptable, interferences in some groundwater samples caused biased high results for arsenic using ICP-MS, which were significantly lower when reanalyzed using hydride generation atomic fluorescence spectrometry. Causes of these interference effects and conclusions from the three case studies to obtain accurate metal data for site assessment, risk characterization, and remedy selection are discussed. © 2010 Wiley Periodicals, Inc. [source] Lead in soil by field-portable x-ray fluorescence spectrometry,an examination of paired In Situ and laboratory ICP-AES resultsREMEDIATION, Issue 3 2008David A. Binstock A major aspect of lead hazard control is the evaluation of soil lead hazards around housing coated with lead-based paint. The use of field-portable X-ray fluorescence (FPXRF) to do detailed surveying, with limited laboratory confirmation, can provide lead measurements in soil (especially for planning abatement activities) in a far more cost-efficient and timely manner than laboratory analysis. To date, one obstacle to the acceptance of FPXRF as an approved method of measuring lead in soil has been a lack of correspondence between field and laboratory results. In order to minimize the differences between field and laboratory results, RTI International (RTI) has developed a new protocol for field drying and sieving soil samples for field measurement by FPXRF. To evaluate this new protocol, composite samples were collected in the field following both U.S. Department of Housing and Urban Development (HUD) guidelines and ASTM International (ASTM) protocols, measured after drying by FPXRF, and returned to the laboratory for confirmatory inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis. Evaluation of study data from several diverse sites revealed no statistical difference between paired FPXRF and ICP-AES measurements using the new method. © 2008 Wiley Periodicals, Inc. [source] Growth factors improve gene expression after lentiviral transduction in human adult and fetal hepatocytesTHE JOURNAL OF GENE MEDICINE, Issue 2 2007Clare Selden Abstract Background Lentiviral vectors may be vectors of choice for transducing liver cells; they mediate integration in quiescent cells and offer potential for long-term expression. In adult liver, hepatocytes are generally mitotically quiescent. There has been controversy as to the necessity for lentiviral vector target cells to be in the cell cycle; currently, there is consensus that effective transduction can be achieved in quiescent hepatocytes, by using virus at high titre. However, transduction approaches which reduce the multiplicities of infection (MOIs) required provide potential benefit of cost and safety for therapeutic use. Methods We used two late-generation HIV-based lentiviral vector systems (pHR-SIN-cppT SGW and pRRLSIN.cPPT.PGK.WPRE) encoding LacZ/GFP reporter genes to transduce adult and fetal human hepatocytes in vitro + /, growth factors, hepatocyte growth factor (HGF) and epidermal growth factor (EGF). Green fluorescent protein (GFP) expression was observed microscopically, and quantified by fluorescence spectrometry for protein expression, fluorescence-activated cell sorting (FACS) analysis to identify the proportion of cells expressing GFP, and real-time quantitative polymerase chain reaction (PCR) for number of integrations. Results Gene expression following lentiviral transduction of human liver cells in vitro was markedly enhanced by the growth factors HGF and EGF. In adult cells growth factors led to a greater proportion of cells expressing more GFP per cell, from more integration events. In human fetal cells, the proportion of transduced hepatocytes remained identical, but cells expressed more GFP protein. Conclusions This has implications for the design of regimes for liver cell gene therapy, allowing marked reduction of MOIs, and reducing both cost and risk of viral-mediated toxicity. Copyright © 2007 John Wiley & Sons, Ltd. [source] First approach of a methodological set-up for selenomethionine chiral speciation in breast and formula milk using high-performance liquid chromatography coupled to atomic fluorescence spectroscopyAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 6 2007J. L. Gómez-Ariza Abstract The chiral speciation of selenomethionine in breast and formula milk based on species separation by high-performance liquid chromatography followed by online microwave-assisted digestion and detection with hydride generation atomic fluorescence spectrometry (HPLC-MAD-HG-AFS) requires severe sample manipulation to avoid matrix influence. Sample clean-up for fat and protein elimination using centrifugation and ultrafiltration was optimized, and selenomethionine preconcentration based on cation exchange solid-phase extraction was studied and optimized. The resulting procedure is suitable for chiral selenium speciation in infant milk with detection limits of 3.1 and 3.5 ng ml,1 as Se for L -selenomethionine and D -selenomethionine, respectively. The time necessary for the analysis, about 90 min, including sample clean-up, analyte preconcentration and chromatographic separation, makes the approach suitable for routine analysis. Copyright © 2007 John Wiley & Sons, Ltd. [source] PROVENANCE STUDIES OF CHALCOLITHIC OBSIDIAN ARTEFACTS FROM NEAR LAKE URMIA, NORTHWESTERN IRAN USING WDXRF ANALYSISARCHAEOMETRY, Issue 1 2010K. A. NIKNAMI In 2005,2006 we initiated a major archaeological survey and chemical characterization study to investigate the long-term use of obsidian along the eastern shores of Lake Urmia, northwestern Iran. Previous research in the area suggested that almost all archaeological obsidian found in this area originated from the Nemrut Da, source located in the Lake Van region of Anatolia (Turkey). More recent research on obsidian artefacts from the Lake Urmia region has identified a significant number of obsidian artefacts with compositions different from the sources near Lake Van. This suggests that the obsidian artefacts are from a yet to be identified geological source, but possibly one that was not too distant. In order to advance our knowledge of Iranian obsidians and eventually refine provenance criteria we analysed obsidian from 22 Chalcolithic sites and some source areas. The compositions of both obsidian source samples and artefacts were determined using wave length dispersive X-ray fluorescence spectrometry (WDXRF). This paper presents results from the trace elemental analysis of both geological and archaeological obsidians, providing important new data concerning the diachronic relationship between lithic technology and raw material in the north-west of Iran. [source] Chemical characterization of ancient pottery from sudan by x-ray fluorescence spectrometry (xrf), electron microprobe analyses (empa) and inductively coupled plasma mass spectrometry (ICP,MS),ARCHAEOMETRY, Issue 3 2004M. Klein Sixty-four sherds and seven natural clays from prehistoric sites in northwestern Sudan have been submitted to petrological and chemical analysis using XRF spectrometry, EMPA and ICP,MS. According to their texture, the sherds form five different groups. The high contents of P2O5 (more than 0.5 wt%) discerned in 19 samples and the variation of the P2O5 content in two samples of the same vessel can be explained by post-depositional processes or by the ancient organic contents (e.g., milk) of the vessel. Chemical classification of the pottery bulk suggests that vessels were made locally, as only sherds from the same area show homogeneity of data. [source] Host,Guest Interaction of Chaperonin GroEL and Water-Soluble CdTe Quantum Dots and its Size-Selective InclusionCHEMPHYSCHEM, Issue 15 2008Chaoqing Dong Abstract Some nanoparticles, such as quantum dots (QDs), are widely used in the biological and biomedical fields due to their unique optical properties. However, little is currently known about the interaction between these nanoparticles and biomolecules. Herein, we systemically investigated the interaction between chaperonin GroEL and water-soluble CdTe QDs based on fluorescence correlation spectroscopy (FCS), capillary electrophoresis, and fluorescence spectrometry. We observed that some water-soluble CdTe QDs were able to enter the inner cavity of GroEL and formed an inclusion complex after the activation of chaperonin GroEL with ATP. The inclusion of GroEL was size-selective to QDs and only small QDs were able to enter the inner cavity. The inclusion could suppress the fluorescence quenching of the QDs. Meanwhile, we evaluated the association constant between chaperonin GroEL and CdTe QDs by FCS. Our results further demonstrated that FCS was a very useful tool for study of the interaction of QDs and biomolecules. [source] | |||||||||||||||||||